[RFC 06/13] v4l2-async: per notifier locking

From: Pavel Machek
Date: Tue Feb 14 2017 - 08:42:15 EST

From: Sebastian Reichel <sre@xxxxxxxxxx>

Without this, camera support breaks boot on N900.

Signed-off-by: Ivaylo Dimitrov <ivo.g.dimitrov.75@xxxxxxxxx>
---
drivers/media/v4l2-core/v4l2-async.c | 54 ++++++++++++++++++------------------
include/media/v4l2-async.h | 2 ++
2 files changed, 29 insertions(+), 27 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-async.c b/drivers/media/v4l2-core/v4l2-async.c
index 96cc733..26492a2 100644
--- a/drivers/media/v4l2-core/v4l2-async.c
+++ b/drivers/media/v4l2-core/v4l2-async.c
@@ -57,7 +57,6 @@ static bool match_custom(struct v4l2_subdev *sd, struct v4l2_async_subdev *asd)

static LIST_HEAD(subdev_list);
static LIST_HEAD(notifier_list);
-static DEFINE_MUTEX(list_lock);

static struct v4l2_async_subdev *v4l2_async_belongs(struct v4l2_async_notifier *notifier,
struct v4l2_subdev *sd)
@@ -102,12 +101,15 @@ static int v4l2_async_test_notify(struct v4l2_async_notifier *notifier,

if (notifier->bound) {
ret = notifier->bound(notifier, sd, asd);
- if (ret < 0)
+ if (ret < 0) {
+ dev_warn(notifier->v4l2_dev->dev, "subdev bound failed\n");
return ret;
+ }
}

ret = v4l2_device_register_subdev(notifier->v4l2_dev, sd);
if (ret < 0) {
+ dev_warn(notifier->v4l2_dev->dev, "subdev register failed\n");
if (notifier->unbind)
notifier->unbind(notifier, sd, asd);
return ret;
@@ -141,7 +143,7 @@ int v4l2_async_notifier_register(struct v4l2_device *v4l2_dev,
{
struct v4l2_subdev *sd, *tmp;
struct v4l2_async_subdev *asd;
- int i;
+ int ret = 0, i;

if (!notifier->num_subdevs || notifier->num_subdevs > V4L2_MAX_SUBDEVS)
return -EINVAL;
@@ -149,6 +151,7 @@ int v4l2_async_notifier_register(struct v4l2_device *v4l2_dev,
notifier->v4l2_dev = v4l2_dev;
INIT_LIST_HEAD(&notifier->waiting);
INIT_LIST_HEAD(&notifier->done);
+ mutex_init(&notifier->lock);

for (i = 0; i < notifier->num_subdevs; i++) {
asd = notifier->subdevs[i];
@@ -168,28 +171,22 @@ int v4l2_async_notifier_register(struct v4l2_device *v4l2_dev,
list_add_tail(&asd->list, &notifier->waiting);
}

- mutex_lock(&list_lock);
+ /* Keep also completed notifiers on the list */
+ list_add(&notifier->list, &notifier_list);
+ mutex_lock(&notifier->lock);

list_for_each_entry_safe(sd, tmp, &subdev_list, async_list) {
- int ret;
-
asd = v4l2_async_belongs(notifier, sd);
if (!asd)
continue;

ret = v4l2_async_test_notify(notifier, sd, asd);
- if (ret < 0) {
- mutex_unlock(&list_lock);
- return ret;
- }
+ if (ret < 0)
+ break;
}
+ mutex_unlock(&notifier->lock);

- /* Keep also completed notifiers on the list */
- list_add(&notifier->list, &notifier_list);
-
- mutex_unlock(&list_lock);
-
- return 0;
+ return ret;
}
EXPORT_SYMBOL(v4l2_async_notifier_register);

@@ -210,7 +207,7 @@ void v4l2_async_notifier_unregister(struct v4l2_async_notifier *notifier)
"Failed to allocate device cache!\n");
}

- mutex_lock(&list_lock);
+ mutex_lock(&notifier->lock);

list_del(&notifier->list);

@@ -237,7 +234,7 @@ void v4l2_async_notifier_unregister(struct v4l2_async_notifier *notifier)
put_device(d);
}

- mutex_unlock(&list_lock);
+ mutex_unlock(&notifier->lock);

/*
* Call device_attach() to reprobe devices
@@ -262,6 +259,7 @@ void v4l2_async_notifier_unregister(struct v4l2_async_notifier *notifier)
}
kfree(dev);

+ mutex_destroy(&notifier->lock);
notifier->v4l2_dev = NULL;

/*
@@ -274,6 +272,7 @@ EXPORT_SYMBOL(v4l2_async_notifier_unregister);
int v4l2_async_register_subdev(struct v4l2_subdev *sd)
{
struct v4l2_async_notifier *notifier;
+ struct v4l2_async_notifier *tmp;

/*
* No reference taken. The reference is held by the device
@@ -283,24 +282,25 @@ int v4l2_async_register_subdev(struct v4l2_subdev *sd)
if (!sd->of_node && sd->dev)
sd->of_node = sd->dev->of_node;

- mutex_lock(&list_lock);
-
INIT_LIST_HEAD(&sd->async_list);

- list_for_each_entry(notifier, &notifier_list, list) {
- struct v4l2_async_subdev *asd = v4l2_async_belongs(notifier, sd);
+ list_for_each_entry_safe(notifier, tmp, &notifier_list, list) {
+ struct v4l2_async_subdev *asd;
+
+ /* TODO: FIXME: if this is called by ->bound() we will also iterate over the locked notifier */
+ mutex_lock_nested(&notifier->lock, SINGLE_DEPTH_NESTING);
+ asd = v4l2_async_belongs(notifier, sd);
if (asd) {
int ret = v4l2_async_test_notify(notifier, sd, asd);
- mutex_unlock(&list_lock);
+ mutex_unlock(&notifier->lock);
return ret;
}
+ mutex_unlock(&notifier->lock);
}

/* None matched, wait for hot-plugging */
list_add(&sd->async_list, &subdev_list);

- mutex_unlock(&list_lock);
-
return 0;
}
EXPORT_SYMBOL(v4l2_async_register_subdev);
@@ -315,7 +315,7 @@ void v4l2_async_unregister_subdev(struct v4l2_subdev *sd)
return;
}

- mutex_lock(&list_lock);
+ mutex_lock_nested(&notifier->lock, SINGLE_DEPTH_NESTING);

list_add(&sd->asd->list, &notifier->waiting);

@@ -324,6 +324,6 @@ void v4l2_async_unregister_subdev(struct v4l2_subdev *sd)
if (notifier->unbind)
notifier->unbind(notifier, sd, sd->asd);

- mutex_unlock(&list_lock);
+ mutex_unlock(&notifier->lock);
}
EXPORT_SYMBOL(v4l2_async_unregister_subdev);
diff --git a/include/media/v4l2-async.h b/include/media/v4l2-async.h
index 8e2a236..690a81f 100644
--- a/include/media/v4l2-async.h
+++ b/include/media/v4l2-async.h
@@ -84,6 +84,7 @@ struct v4l2_async_subdev {
* @waiting: list of struct v4l2_async_subdev, waiting for their drivers
* @done: list of struct v4l2_subdev, already probed
* @list: member in a global list of notifiers
+ * @lock: lock hold when the notifier is being processed
* @bound: a subdevice driver has successfully probed one of subdevices
* @complete: all subdevices have been probed successfully
* @unbind: a subdevice is leaving
@@ -95,6 +96,7 @@ struct v4l2_async_notifier {
struct list_head waiting;
struct list_head done;
struct list_head list;
+ struct mutex lock;
int (*bound)(struct v4l2_async_notifier *notifier,
struct v4l2_subdev *subdev,
struct v4l2_async_subdev *asd);
--
2.1.4


--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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